Refractory conductor.



W. D. COOLIDGE.

BEFRAGTORY CONDUGTOR.

APPLICATION PILD AUG. 1, 1906. BENEWED DEO. 8, 1910. 1,026,429, Patend May 1 4, 1912.

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UNITED sTATEs PATENT OFFICE.

WILLIAM D. COOLIDGE, OF SCHENECTADY, NEW IYORK, ASSIGNOR T0 GENERAL 'ELECTRIC COMPANY, A CORPORATION OF NEW YQRK.

Speciflcation of Letters Patent.

Patented May 14, 1912.

Application filed. August 1, 1906, Serial No. 328,726. Renewed December 8, 1910. Serial No. 596,373.

To all fw/to'mI z't may cancer-n:

Be it known that I, WILLIAM D. CooLiDoE, a citizen of the United States, residlng at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Ilnprovements in Refractory Conducto-rs, of which the following '1s a speclfication. n

This invention relates to the production of refractory electrical conductors suitable* for use in incandescent lamps, electric furnaces, and other apparatus. g

It comprises a process whereby refractor material, even though non-ductlle, may be shaped into wires, plates, rods, or other forms, and then consolidated 1nto a coherent conductor capable of converting electrlcal energy into light at enormously hlgh temperatures.

According to my inventlon, a refractory element, alloy, compound or mlxture 1s 1mpregnated with a ductile metal or alloy, and the product so obtained is slntered together and consolidated by the passage of current therethrough, either before or after meclianical manipnlations of the materlal, such as rolling, drawing, squlrting, etc.

My process is applicable to a Agreat variety of refractory metals and materials, such for instance, as tungsten, molybdenum, boron, zirconium, titanium, or compounds or alloys of any of these, or of other material of the same general refractory nature. The less refractory metals or alloys with which these refractory materials are 1mpregnated, may be such metals as copper, cadmium, gold, silver, mercury, 'b1smuth, tin, and various other of the well known metals having Vaporizing points approximating those of the metals above named; or I may use amalgams or other alloys of these metals, such for instance as cadmium, amalgam, bismuth-cadmium alloy or =bismuthcadmium-mercury alloy, etc. In general, the less refractory metals are introduced into the pores of the refractory material and serve to give the body ductility and strength, and in some cases to increase its electrical conductivi'ty. The ductile or low melting metal is retained in this position until the body has beenjworked or formed into the desired shape and it is then driven out by heat treatment to leave behind a refractory wire or rod.

My process may be carried out with the aid of divers forms'of apparatus, 'but Ihave shown in the drawings forming a part of this specification, one means for efecting the desired result, and in the following descrlptlon I- have indicated 'other means for o arrying out the general idea of my inven- In the drawings, Figure 1 is an elevaton of one type of electric furnace in which the impregnati'ng process may be effected; F ig. 2 is a sectional elevaton of a crucible and 1ts charge, suitable for use in an electric furnace of somewhat different construction.

In F ig. 1, a hermetically sealed chamber l of glass or other suitable material, is pro-- vided at its top with an opening 2 through which passes a metal rod orplunger 3, carrying at its lower end a plurality of clips 4, which engage With one end of a block or rod orefractory material to be treated. This block or rod consists of pure tungsten powder pressed into shape under heavy pressure, though it is to be understood that other materials than tungsten may be treated in a similar manner, or that the rod may be made by other known methods. The rod or plunger 3 passes into the chamber through a rubber pressure tubing 6 and makes an air tight joint therewith so that it may be raised or lowered without materially afi'ecting the state of the vacuum within the chamber. The rod also serves to establish an electrical connection to the tungsten block for purposes hereinafter set forth. The tube 01' chamber 1 is permanently connected to a suitable vacuum pump so that the gases or vapors given off during the treatment may readily be removed. At the bottom of the chamber or envelop 1 is placed a quantity of the ductile metal, amalgam or alloy with which the tungsten is to be impregnated. If this metallic material is not liquid at ordinary temperatures, I may heat the lower` end of the tube with a flame or with a suitable liquid bath 8. .This bath may consist of molt'en type metal, lead, or even of higher melting elements or compounds, provided the temperature does not exceed that at which the glass or other envelop will successfully operate. Electrical connect-ion may be established to the metal 7 through suitable lead wires 9 passing through the envelop. In utilizing this apparatus, I first exhaust the air from the chamber and then lower the plunger With its supported rod or block of'tungsten until the latter makes contact with' the liquid metal in the lower part of the envelop. The

- lunger is then lifted and' an arc established etween thetungsten rod and the vaporizable metal atxthe bottom of the tube. Preferably this metal acts as the cat-hode for a direct current arc. The tungsten rod, when subjected as anode to the heating action of the lnetallic a-rc, gives ofl' considerable quant-ities of occluded air and ,other gases, and these are taken out through the pump, so that after some minutes of operation the tungsten rod is in a clean and porous condition and well adapted to receive metal within its pores. When this condition is reached I suddenly lower the tungsten rod into the liquid metal and permit the ductile metal to percolate through the tungsten and completely fill up all the minute spaces in the stick. It is not necessary that all the tungsten rod should be submerged in the fused metal as I find that the ductile metal is drawn up by capillary or similar forces into all parts of the stick which have been highly lieated. I next withdraw 'the impregnated stick fromthe liquid, and -after cooling, I remove it from the tube and break away the extreme end which was in contact with the spring clips 4, for fear that this end might perchance have been contaminated by contact with the clips. The resulting stick is smooth and strong, has a fine even fracture and may readilylbe polished. I find that the quantity of ductile metal taken up by the refractory pressed stick depends on the degree of subdivision of the refractory powder and also on the extent to which it has been comp `ressed.v The, color of the resulting stick is also depe'ndefnt:` on the ductile metal used; in general thei1 n `-l pregnated material resembles 'the 'ductile' material. Tungsten impregnated withlsilve'r or cadmium is white, while tungsten lor tl`1' ra. other refractory metals become yellow :vor salmon colored when impregnated' with cop-.

per.

ductile metals which fuse at temperatures somewhat higher than would be conveniently obtained in the apparatus-shown in Fig. 1, I utilize the crucible shown inFig. 2,

together with a vacuum furnaceof the type' shown in United States Patent 'to'Arsem No..

785,535, March 21, 1905.V The crucible 10, shown in Fig. 2, may consist of graphite, alumina or other material which isin'ert with respect to the materials v.under treatment, at the temperature of treatment. The ductile or fusible metal 11 is placed in the crucible, together with the pressed or molded stick of refractory material. The crucible is then introduced in the vacuum furnace, the air exhausted, and the temperature raised to the point at which gases are lib- In impregnating with copper and other:

erated from the stick under treatment- I prefer, however, not to raise the temperature of treatment high enough to liquefy the ductile metal until after all 'the gases have been pumped from the refractory stick. When, however, the ,material becomes free from occluded gases and volatile matter, I raise the temperature to liquefy the fusible metal 11, whereupon the refractory stick soaks up relatively large quantities thereof. Even 'with sticks several inches longthe liquefied metal diffpuses to the extreme upper end of the stick. I next allow the crucible to cool and when it can safelybe removed from the furnace I break away the treated stick from the unused ductile metal and then have a product similar to that obtained by the apparatus shown in 'I`ig. 1.

The impregnated sticks above described I tion of a high current. To do this, Iprolvide them with suitable terminals, mount them in va vacuum or an inert atmosphere, and pass suflicient current through the sticks to vaporize the less refractory metal or alloy, and leave behind a coherent sintered mass. of refractory material. Whatever the principle may be which underlies this phenomenon, I find that if the current is properly applied, the resultant stick is much stronger and better su'ited for use as glowers than the original stick of pres'sed or untreated material. My process is'not, however, limited to the production of refractory glow bodies of relatively large cross-section,

as I find that the impregnated sticks may be rolled, drawn, or extruded much like pure 'metals of fair ductility, and that by careful Vhandling I can convert the sticks into plates v-or foil or into wires and strips of substantially the size now used' in incandescent lamps. I 'All this may be done, even though the original refractory stick is pressed up from a lnon-coherent and finely divided powder. After obtaining wires of the desired size and shape, I drive out the ductile metal by curvrent passed therethrough, and I sinter the refractory particles together so strongly that vthe resulting filament appears to be a compact uniform wire of homogeneous structure. IfV I work with material as refractory as tungsten, titanium or other metals above enumerated, the refractory filamentsproduced may be operated in an lincandescent lamp at an exceedin'gly high efliciency.

The rolling, drawing, or extruding operations above mentioned may under certain circumstances be facilitated by heating the material under treatment, and also by heating the rolls or dies through which it-passes.

In fact, when pressing or squirting a stick impregnated with such materials as copper, cadmium, amalgam, etc., I consider that the "da nger of fracturing the die maybe .greatly v lessened by subjecting the stick to considerable heat, though I am careful not to apply enough heat to break up the bond between the ductile metal or alloy and refractory particles,. or in any way to 'interfere with the production of a smooth, strong and uniform Wire or thread of squirted material.

I have |above described the impregnation of a compressed body of refractory powder by heat treatment in a vacuum followed by contactA with a bathbf biSmuth-cadmium alloy, and have presented claims on the complete process as described. In another applicati-o-n Serial No. 377,781, filed by me June 7, 1907, I have presented claims of a somewhat general nature on the production of a mixture of a refractory material with biSmuth-cadmium amalgam and on the production of lamp filaments therefrom, together with suitable claims on the product.

What I'claim as new and desire to secure by Letters Patent of the United States is,-

1. The process which consists in Shaping a body from refractory material, impregnating said body with a metallic material having a relat-ively low vaporizin temperature, and subsequently heating sald product by current passed therethrough to vaporize said metalhc material and consolidate said body. i

2. The process-which consists in compress-l ing a refractory powder into a rigid body, impregnatingsaid body with ductile metal, and subsequently passing current through said body to vaporize said ductile metal -and consolidate said body.

3. The process which consists in compressing a refractory material into a predetermined Shape, heating said material in a *vacuum to remove gases therefrom, impreg- 'nating with a ductile metalllc material, and

subsequently driving out said ductile material by current passed through said body.

- 4. The process which consists in Shaping a rigid body from refractory powder, heating said body in a vacuum to remove gases therefrom, immersing a port-ion of said body in a fused' metallic material to impregnate said body with said material, Shaping the resultant product into conductors, and subsequently heating said conductors to drive the easily fusible components therefrom.

5. The process which consists in impregnating a stick of refractory material Iwith a less refractory metallic material, Shaping the product so formed into conductors, and

subsequently treating .to remove allicomponents except said more refractory material;

6. The sub-process which consists in compressing refractory material into a stick, im-4 pregnating said stick with a ductile metallic material, and squirtlmg the product so obtained to produce wires.

7 The process which consists in compressing refractorybjmat'erial into a stick, impregnating said Stick with a ductile metallic material, squirting the product so obtained to produce wires, and heating 'Said wires to remove all easily vaporizable components therefrom.

8. The process which consists in compressjingl a refractory powder into a rigid body,

impregnating said body with a ductile metal,

and subsequently heating said body to vaporize said ductile metal and consolidate .said body.

9. The process which consists in compressing a refractory powder into a predetermined Shape, heating said material in a vacuum 'to remove gases therefrom, then bringing said material into contact with a fusible metallic material to impregnate it therewith, and subsequently driving out said fusible mate- ,rial.

10. The process which consists in`comvacuum to remove gases therefrom, impregnating said material with a vductile amalgam, Shaping the product So formed to produce wires, `and. subsequently heating to drive outl the components of said amalgam.

In witnesswhereof, I have hereunto set my hand this 30th day of July, 1906.

WILLIAM D. COOLIDGE.

Witnesses:

BNJAMIN B. HULL, GiiAon M. HANIGAN. 

